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Thread: 27 J sprocket shaft outer bearing race

  1. #1

    Default 27 J sprocket shaft outer bearing race

    I have had some dificulty removing the sprocket shaft bearing outer race from the crank case. I build a tool constructed from a round piece if steel into which holes were drilled that took the handles of 4 pin punches that lined up with the holes on the back of the case. The case was then heated but the race would not budge.
    Eventually i ground down the inside of the race with a diamond grinder to see if it would release.
    It still wouldnt budge intially but after i let the case sit on the gas burner of my domestic stove for half an hour it eventually started to move but it fought me all of the way including breaking three of the pin punches on the way.
    It also trashed the threads in the holes.
    When it eventiually came free i could see what the problem had been. At some point the race had been refitted wrapped in a 1 thou thick brass bush. There was a residue in the case which suggested that some kind of glue had also been used.
    Attached pictures of the race , foil bush and the crank case aperture.
    The new bush will slide into the case without any force and has lateral play where the apertue is now too big which i guesss had been the problem last time it was fixed. I need to stop the race from slopping about in the case and to enable it to be lined up properly.
    I was just wondering whether there was any alternative to using another bit of thin brass.
    I did wonder whether it would be better to ream out the aperture further and then fit a rather thicker aluminium bush which would restore the interference fit for the bearing race.
    I should be gratful to hear from anybody who has had a similar problem or for any suggested solutions.
    As for the four holes i will try and recut the threads but if that doesnt work then i guess they will need to be helicoiled.

    Thanks

    Martin
    in the UK
    Attached Images Attached Images

  2. #2
    Join Date
    Jan 2003
    Location
    England
    Posts
    1,312

    Default

    Dear Martin, new bushings are now being made in 2 and 5 thousandths oversizes, which I would say is the way to go.

  3. #3

    Default

    Steve,
    Thanks for that tip. Never thought to look for that option but that should do the trick.
    Appreciate your input as always
    Regards
    Martin

  4. #4

    Default

    it like a wheel bearing race,take a mig welder and run a bead on race inside.then while hot drive it out.the welding will shrink race.just like when removing wheel bearing races in aluminum wheels

  5. #5
    Join Date
    Aug 2013
    Location
    1 mile east of the Rocky Mountains.
    Posts
    868

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